Kayin Amoh, initially portrayed as a Scottish bounty hunter before being reestablished as English, inherits a mythic legacy as a descendant of a Knight of the Round Table, wielding Excalibur. His biological father’s assassination by Amou—an Organization operative who adopted Kayin in remorse—led to his rigorous training alongside Eiji Shinjo under their mentor Sho Shinjo. After Sho vanished and later killed Amou during a tournament, Kayin entered the first Toshindaibukai seeking vengeance, fracturing his bond with Eiji upon uncovering Sho’s culpability.

Coerced into the second tournament when the Secret Society abducted his adoptive daughter Naru—a child he raised after inadvertently causing her biological father’s death—Kayin helped dismantle the Society and reclaim her. Pursued anew by the Organization, he joined the third tournament, discovering Amou had sacrificed himself to shield Kayin from the Organization’s corrupt rituals. This revelation reconciled him to his foster father’s memory, yet he severed ties with Naru to protect her, leaving her at an orphanage with Excalibur before vanishing.

His journey navigates cycles of vengeance and atonement, mirrored in his namesake allusion to Cain and vegetarianism—a conscious repudiation of violence. Battles staged in crumbling cityscapes parallel his struggle against systemic decay. Once revenge-driven, his arc shifts toward safeguarding others, particularly Naru, while confronting the ethical ambiguities of his profession.

Kayin’s combat fuses acrobatic kicks with electrically charged techniques such as Sonic Slash and Deadly Raise. His aesthetic varies across adaptations, from a red leather jacket to a Michael Jackson-inspired “Beat It” ensemble in the OVA. Later lore ambiguously implies his fate, his absence in subsequent events and a ghostly cameo in Naru’s ending suggesting a possible demise.